Apparatus for manufacturing float glass

ABSTRACT

An apparatus for manufacturing a float glass, including a float bath for storing a molten metal on which a molten glass flows, wherein the molten metal flows in the float bath, comprises a discharge slot having substantially the same size as width of the molten glass to discharge a molten metal crashing against a wall of a downstream end of the float bath and dross floating on the molten metal, and formed through the wall substantially parallel to a traveling direction of the molten glass; connecting channels for communicating the discharge slot with both sides of the float bath; and dross collecting members for collecting the dross.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No.10-2009-0011981 filed in Republic of Korea on Feb. 13, 2009, the entirecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for manufacturing a floatglass, and more particularly, to an apparatus for manufacturing a floatglass using a float glass process.

2. Description of the Related Art

Generally, an apparatus for manufacturing a float glass (also known as asheet glass, a flat glass or a plate glass) using a float glass processis used to manufacture a continuous sheet of glass having a ribbon shapeof a predetermined width by continuously supplying a molten glass onto aflowing molten metal (a molten tin and so on) stored in a float bathwhile floating the molten glass on the molten metal to form a moltenglass ribbon reaching around an equilibrium thickness due to the surfacetension and gravity, and pulling up the molten glass ribbon toward anannealing lehr near an exit of the float bath.

Here, the molten metal includes, for example, a molten tin or a moltentin alloy, and has a greater specific gravity than the molten glass. Themolten metal is received in a float chamber where a reducing atmosphereof hydrogen (H₂) and/or nitrogen (N₂) gas is introduced. The float bathin the float chamber is configured to contain the molten metal therein.The float bath has a horizontally extending structure, and includes ahigh heat resistant material (for example, bottom blocks) therein. Themolten glass forms a molten glass ribbon on the surface of the moltenmetal while moving from an upstream end of the float bath to adownstream end. The molten glass ribbon is lifted up at a location seton the downstream end of the float bath, so called a take-off point, tobe removed from the molten metal, and delivered to an annealing lehr ofa next process.

However, because the molten metal in the float chamber is in ahigh-temperature state (for example, about 600 to 1100° C.), chemicalreactions take place among the molten metal, the molten glass, H₂ and N₂of the atmosphere, a very small amount of O₂, H₂O and S to generateimpurities that are referred to as “dross”. In particular, temperatureis lower at and around the take-off point on the downstream end (ColdEnd) of the float bath than the upstream end (Hot End). Thus, solubilityof the molten metal decreases on the downstream end, and consequently,metal oxide dross, for example SnO₂, etc. is liable to happen andaccumulate on the downstream end. When the molten glass ribbon is liftedup from the take-off point, the dross is attached to the bottom of themolten glass ribbon and drawn from the float bath, accompanied by themolten glass ribbon. As a result, it causes scratch, stain and so onthat may unfavorably influence a subsequent process and/or the qualityof float glass products.

To solve the problems, various techniques have been developed so far.For example, as disclosed in Japanese Patent Publication No. SO45-30711,a conventional apparatus for manufacturing a float glass includes acollecting channel having an approximately T-shaped pocket of which aplane expands slightly in a widthwise direction by a side wall and arear wall of a longitudinal end portion of a float bath. The collectingchannel is formed at a predetermined angle so that dross gathered in thecollecting channel from an exposed drainage area can be guided to thepocket. The dross is discharged from the pocket outside the float bath.

As disclosed in Japanese Patent Laid-open Publication No. 2000-128552,another conventional apparatus for manufacturing a float glass includesa first flow channel extending in a cross direction with respect to adraw-out direction of the float glass, and a second flow channelconnected to an end of the first flow channel and communicated with adam starting from the outside of a side wall. The apparatus flows back amolten metal from a downstream end of a float bath to an upstream endthrough separate flow channels.

However, these conventional techniques remove dross, which was caused bycontamination in a float bath, at both sides of a downstream end of thefloat bath. However, the conventional techniques have difficulty inremoving dross accumulated under the center of a molten glass ribbon atthe downstream end, and to remove such dross, it should open a sidesealing with a separate strap-shaped tool made of wood. Under thisoperational environment, when the side sealing is open, the float bathmay be further contaminated and safety in operation may be notguaranteed. As a result, it may deteriorate the quality of float glassproducts and the procedural stability.

SUMMARY OF THE INVENTION

The present invention is designed to solve the above-mentioned problems,and therefore it is an object of the present invention to provide animproved apparatus for manufacturing a float glass, which has adischarge slot of a substantially same size as width of a molten glassin the widthwise direction of a ‘lip block’ located at a downstream endamong floor blocks of a float bath. The apparatus flows back the moltenmetal flown in through the discharge slot toward the sides of the floatbath, thereby stably removing dross floating on the molten metal.

To achieve the object, an apparatus for manufacturing a float glassaccording to the present invention, including a float bath for storing amolten metal on which a molten glass flows, wherein the molten metalflows in the float bath, comprises a discharge slot having substantiallythe same size as width of the molten glass to discharge a molten metalcrashing against a wall of a downstream end of the float bath and drossfloating on the molten metal, and formed through the wall substantiallyparallel to a traveling direction of the molten glass; connectingchannels for communicating the discharge slot with both sides of thefloat bath; and dross collecting members for collecting the drossflowing through the connecting channels.

Preferably, the discharge slot has an inlet having substantially thesame height as the level of the molten metal to allow an overflow of themolten metal; and a slope surface slanted away from the inlet.

Preferably, each of the dross collecting members comprises a collectingbox provided at one side of the downstream end of the float bath andcommunicated with the corresponding connecting channel; and a paddleinstalled rotatably at an entrance of the collecting box for scrapingthe dross floating on the molten metal flown back along one side of thefloat bath and collecting the dross in the collecting box.

Preferably, the apparatus of the present invention further comprises aheating unit for heating the molten metal flowing through the dischargeslot and the connecting channels.

Preferably, the heating unit has a heater.

EFFECTS OF THE PRESENT INVENTION

The apparatus for manufacturing a float glass according to the presentinvention effectively flows back dross (impurities) accumulated near alip block at a downstream end of a float bath toward both sides of thefloat bath, thereby improving the quality of float glass products andensuring the procedural stability.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the preferred embodiments of thepresent invention and are included to provide a further understanding ofthe spirit of the present invention together with the detaileddescription of the invention, and accordingly, the present inventionshould not be limitedly interpreted to the matters shown in the drawings

FIG. 1 is a schematic plan view of an apparatus for manufacturing afloat glass according to a preferred embodiment of the presentinvention.

FIG. 2 is a side view of FIG. 1.

FIG. 3 is a schematic cross-sectional view of a dross collecting memberof FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Priorto the description, it should be understood that the terms used in thespecification and the appended claims should not be construed as limitedto general and dictionary meanings, but interpreted based on themeanings and concepts corresponding to technical aspects of the presentinvention on the basis of the principle that the inventor is allowed todefine terms appropriately for the best explanation. Therefore, thedescription proposed herein is just a preferable example for the purposeof illustrations only, not intended to limit the scope of the invention,so it should be understood that other equivalents and modificationscould be made thereto without departing from the spirit and scope of theinvention.

FIG. 1 is a schematic plan view of an apparatus for manufacturing afloat glass according to a preferred embodiment of the presentinvention. FIG. 2 is a side view of FIG. 1.

Referring to FIGS. 1 and 2, the apparatus 100 for manufacturing a floatglass according to an embodiment of the present invention is configuredto manufacture a float glass using a so-called float glass process. Theapparatus 100 includes a float chamber, and the float chamber has afloat bath 110 located at a lower portion thereof and a roof 120covering the top of the float bath 110. The float chamber is an airtighttype that has an input port (not shown) and an output port 112.

The float bath 110 stores a molten metal (M) such as a molten tin, amolten tin alloy and so on. The molten metal (M) is supplied from anupstream end of the float bath 110 (shown at the left side of thedrawing) and moves to a downstream end (shown at the right side of thedrawing) by a molten glass (G). The molten metal (M) flows from theupstream end of the float bath 110 to the downstream end due to atemperature gradient in the float bath 110 and at the same time, flowsfrom the center of the float bath 110 to both sides of the float bath110. The temperature gradient is a difference in temperature between thedownstream end and the upstream end which is maintained at a relativelyhigher temperature. The molten glass (G) also flows from the upstreamend of the float bath 110 to the downstream end, and is pulled upwardsat a take-off point (TO) to be removed from the surface of the moltenmetal (M) and then drawn out toward an annealing Lehr (not shown) of anext process (See arrow C).

The atmosphere in the float chamber is formed by a mixed gas of nitrogenand hydrogen. The mixed gas is maintained at pressure slightly higherthan the external atmosphere, and the molten metal (M) and a ribbon ofthe molten glass (G) are maintained at about 800 to 1300° C. by anelectric heater (not shown). The molten glass (G) is a nonalkalineglass, a soda-lime glass, and so on. The principle and structure forflow generation of the molten metal (M) in the float bath 110, andinput, ribbonization, movement and discharge of the molten glass (G) arewell known in a typical float glass process, and the detaileddescription is omitted herein.

The float bath 110 has a discharge slot 130, connecting channels 140 anddross collecting members 150. The discharge slot 130 runs throughapproximately entirely a wall of the downstream end, or a lip block 114.The connecting channels 140 are communicated with the discharge slot 130and the sides of the float bath 110. The dross collecting members 150are configured to collect a molten metal (M) and dross (D) flown throughthe connecting channel 140.

The discharge slot 130 is configured to discharge the molten metal (M)crashing against the center of the lip block 114 that is a wall of thedownstream end, and dross (D) that may float on the molten metal (M).The discharge slot 130 has a predetermined size that is slightly shorterthan the width of a molten glass (G) relative to the edge of the lipblock 114. That is, the discharge slot 130 is formed to have apredetermined width and a substantially rectangular cross section.

The discharge slot 130 has an inlet 132 and a slope surface 134. Theinlet 132 has substantially the same height as the level of the moltenmetal (M) to allow an overflow of the molten metal (M). The slopesurface 134 is slanted away from the inlet 132. Preferably, a maximumdepth of the slope surface 134 is substantially equal to the depth ofthe float bath 110.

The connecting channels 140 communicate with the discharge slot 130, andare formed inside of the lip block 114 substantially parallel to thewidthwise direction of the float bath 110 so as to flow back the moltenmetal (M) and impurities or dross (D) flown in through the dischargeslot 130 toward both sides of the float bath 110. And, the connectingchannels 140 are connected with side holes 142 communicated with theboth sides of the float bath 110.

The discharge slot 130 and the connecting channels 140 may be formed bymodifying the lip block 114 and piping to the modified lip block, or maybe designed and formed from the beginning.

As shown in FIG. 3, each of the dross collecting members 150 comprises acollecting box 152 and a paddle 154. The collecting box 152 is locatedat each opposing side of the downstream end of the float bath 110 andcommunicated with the corresponding connecting channel 152. The paddle154 is rotatably installed at or near an entrance of the collecting box152 to scrape the dross (D) floating on the molten metal (M) flown backalong the both sides of the float bath 110 and to collect the dross (D)in the collecting boxes 152.

The collecting box 152 is provided separately from the float bath 110,and has a sufficient size to receive the flow of molten metal (M)flowing back from the downstream end of the float bath 110. Preferably,the same airtight atmosphere as the float bath 110 is created in thecollecting box 152. The collecting box 152 has a separate door (notshown) capable of selectively opening in order to completely remove thedross (D) flown therein from the float bath 110.

The paddle 154 has a plurality of blades 158 about a rotation axis 156installed in the side wall of the collecting box 152. The rotation axis156 is rotated at a predetermined rate by a driving source 155 such as amotor or the like. The blades 158 are arranged such that their rotatingedges are substantially at the same location as the level of the moltenmetal (M) at the entrance of the collecting box 152. In other words, thelocation relationship between the edges of the blades 158 and the moltenmetal (M) is sufficient if the dross (D) floating on the molten metal(M) can be scraped and collected in the collecting box 152 by the paddle154 without any substantial influence on the flow of the molten metal(M) when the blades 158 rotate by rotation of the rotation axis 156.

According to the above-mentioned embodiment, the dross (D) generated atand around the take-off point (TO) of the float bath 110 flows fartherto the downstream end through the discharge slot 130 and then flows backto both sides of the downstream end of the float bath 110 through theconnecting channels 140. Through this flow-back process, the dross (D)flows into the collecting box 152 by rotation of the blades 158 of thepaddle 154. Thereby a kind of ceiling is formed by the lip block 114 atthe discharge slot 130 and the top of the connecting channels 140.Accordingly, it can prevent dross (D) existing on a traveling route ofthe molten glass (G) from attaching to the flowing molten glass (G). Inparticular, it can prevent attachment of the dross (D) throughout theentire width of the molten glass (G), thereby reducing a defective rateof float glass.

Meanwhile, the dross (D) floating on the molten metal (M) may becollected by a separate collecting means (not shown). The collectingmeans may be provided near the discharge slot 130 or the connectingchannels 140, or at each opposing side of the downstream end of thefloat bath 110. Here, the collecting means may include, for example, anequipment for decomposing dross (D) by heating the molten metal (M), anequipment for separating dross (D) by cooling the molten metal (M) andmechanically capturing the separated dross (D), and so on.

According to the embodiment of the present invention, the apparatus 100for manufacturing a float glass may further comprise heating units 160.The heating units 160 are arranged at the corresponding connectingchannels 140 to increase the temperature of the molten metal (M) thatwas cooled while flowing along the connecting channels 140. The heatingunits 160 may be an electric heater, and are configured to solve theproblem that an unnecessary gas may be produced due to the decreasedtemperature of the molten metal (M) at the downstream end of the floatbath 110.

In an alternative embodiment of the present invention, the float bath110 may further have a linear motor (not shown) for generating a backflow of the molten metal (M) and the dross (D) in the discharge slot 130and the connecting channels 140 by applying a traveling magnetic fieldto the molten metal (M) flown in through the discharge slot 130. Thelinear motor may be provided with an arbitrary number on the surface ofthe molten metal (M), or at the side, the bottom or other locations inthe discharge slot 130 and/or the connecting channels 140 of the floatbath 110. The linear motor can directly drive the molten metal (M) in anoncontact manner, and thus it has an advantage of easy flow control.The linear motor generates a traveling magnetic field in a predetermineddirection by forming a comb-shaped primary coil around a core, applyinga three-phase alternating current voltage to the coil, and magnetizingthe coil. The generated traveling magnetic field provides a drivingforce to the molten metal (M). The flow control of the molten metal (M)may be preset before operation of the apparatus for manufacturing afloat glass or may be set in the middle of producing a glass afteroperation of the apparatus for manufacturing a float glass according tonecessity. When the linear motor operates to excite the travelingmagnetic field, a back flow of the molten metal (M) is generated in thedischarge slot 130 and the connecting channels 140. That is, the moltenmetal (M), on which dross may float, passes through the discharge slot130 from the downstream end, moves along the connecting channels 140 andflows back to both sides of the float bath 110 through the side holes142.

Meanwhile, the present invention is not limited to the above-mentionedembodiments, and proper modifications and improvements may be madethereto. And, it is possible to arbitrarily select the material, shape,size, type, number, location, etc. of the float bath, the molten metal,the molten glass, the take-off point, the discharge slot, the connectingchannels, the dross collecting members, etc. within the ranges toachieve the object of the present invention, however the presentinvention is not limited in this regard.

As mentioned above, the apparatus for manufacturing a float glassaccording to the present invention flows back the molten metal to bothsides of the float bath through the discharge slot and the connectingchannels and collects dross floating on the molten metal using the drosscollecting members. Accordingly, it can prevent dross on the moltenmetal from staying at the downstream end of the float bath and reduce adefect rate of float glass.

Hereinabove, the present invention is described with reference to thelimited embodiments and drawings. However, the description proposedherein is just a preferable example for the purpose of illustrationsonly, not intended to limit the scope of the invention, so it should beunderstood that other equivalents and modifications could be madethereto without departing from the spirit and scope of the invention.

1. An apparatus for manufacturing a float glass, including a float bathfor storing a molten metal on which a molten glass flows, the moltenmetal flowing in the float bath, the apparatus comprising: a dischargeslot running through approximately entirely an end wall of a downstreamend of the float bath and having a predetermined size that is slightlyshorter than a width of the molten glass to discharge the molten metalcrashing against the end wall and dross floating on the molten metal;connecting channels for communicating the discharge slot with both sidesof the float bath; and dross collecting members for collecting the drossflowing through the connecting channels.
 2. The apparatus formanufacturing a float glass according to claim 1, wherein the dischargeslot has: an inlet having substantially the same height as the level ofthe molten metal to allow an overflow of the molten metal; and a slopesurface slanted away from the inlet.
 3. The apparatus for manufacturinga float glass according to claim 1, wherein each of the dross collectingmembers comprises: a collecting box provided at one side of thedownstream end of the float bath and communicated with the correspondingconnecting channel; and a paddle installed rotatably at an entrance ofthe collecting box for scraping the dross floating on the molten metalflown back along one side of the downstream end of the float bath andcollecting the dross in the collecting box.
 4. The apparatus formanufacturing a float glass according to claim 1, further comprising: aheating unit for heating the molten metal flowing through the dischargeslot and the connecting channels.
 5. The apparatus for manufacturing afloat glass according to claim 4, wherein the heating unit has a heater.